KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > net > sf > jga > fn > comparison > ComparatorFn


1 // ============================================================================
2 // $Id: ComparatorFn.java,v 1.12 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2002-2005 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // available from Sun Microsystems, Inc.
10 //
11 // http://www.sun.com/cddl/cddl.html
12 //
13 // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14 // publish revised and/or new versions of the License. You may not use,
15 // distribute, or otherwise make this file available under subsequent versions
16 // of the License.
17 //
18 // Alternatively, the contents of this file may be used under the terms of the
19 // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20 // case the provisions of the LGPL are applicable instead of those above. If you
21 // wish to allow use of your version of this file only under the terms of the
22 // LGPL, and not to allow others to use your version of this file under the
23 // terms of the CDDL, indicate your decision by deleting the provisions above
24 // and replace them with the notice and other provisions required by the LGPL.
25 // If you do not delete the provisions above, a recipient may use your version
26 // of this file under the terms of either the CDDL or the LGPL.
27 //
28 // This library is distributed in the hope that it will be useful,
29 // but WITHOUT ANY WARRANTY; without even the implied warranty of
30 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31 // ============================================================================
32
33 package net.sf.jga.fn.comparison;
34
35 import net.sf.jga.fn.BinaryFunctor;
36 import java.io.Serializable JavaDoc;
37 import java.util.Comparator JavaDoc;
38
39 /**
40  * Functor wrapper around Comparator object. Allows Comparators to be used
41  * anywhere a Functor returning an Integer could have been used. Also
42  * implements Comparator as well, so an instance of this class could be used
43  * anywhere that the constructor argument could be used.
44  * <p>
45  * To Serialize a ComparatorFn, the Comparator given at construction must be
46  * Serializable.
47  * <p>
48  * Copyright &copy; 2002-2005 David A. Hall
49  *
50  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
51  **/
52
53 public class ComparatorFn<T> extends BinaryFunctor<T,T,Integer JavaDoc> implements Comparator JavaDoc<T> {
54
55     static final long serialVersionUID = -7851342943467256913L;
56
57     private Comparator JavaDoc<T> _comp;
58
59     /**
60      * Builds the ComparatorFn wrapped around the given Comparator.
61      *
62      * @throws NullPointerException if no Comparator is passed.
63      */
64     public ComparatorFn(Comparator JavaDoc<T> comp) {
65         if (comp == null) {
66             throw new IllegalArgumentException JavaDoc("Comparator may not be null");
67         }
68         
69         _comp = comp;
70     }
71
72     /**
73      * Returns the comparator in use by this functor
74      */
75     public Comparator JavaDoc<T> getComparator() { return _comp; }
76
77     // BinaryFunctor interface
78
79     /**
80      * Given arguments <b>x</b> and <b>y</b>, return the result of the
81      * Comparator's <code>compare(x,y)</code> method, wrapped in an Integer.
82      * Whether or not a NullPointerException is thrown if either x or y are
83      * null is up to the Comparator
84      *
85      * @return the result of the Comparator's <code>compare(x,y)</code> method
86      */
87     public Integer JavaDoc fn(T x, T y) {
88         return new Integer JavaDoc(compare(x, y));
89     }
90     
91     /**
92      * Calls the Visitor's <code>visit(ComperatorFn)</code> method, if it
93      * implements the nested Visitor interface.
94      */
95     public void accept(net.sf.jga.fn.Visitor v) {
96         if (v instanceof ComparatorFn.Visitor)
97             ((ComparatorFn.Visitor)v).visit(this);
98         else
99             v.visit(this);
100     }
101
102     // Comparator interface
103
104     public int compare(T x, T y) {
105         return _comp.compare(x, y);
106     }
107
108     // Object overrides
109
110     public String JavaDoc toString() {
111         return "ComperatorFn";
112     }
113     
114     // AcyclicVisitor
115
116     /**
117      * Interface for classes that may interpret a <b>ComparatorFn</b> functor.
118      */
119     public interface Visitor extends net.sf.jga.fn.Visitor {
120         public void visit(ComparatorFn host);
121     }
122 }
123
124
125                                       
126
Popular Tags